Beginning the detailing

Ok, at the front of the car, position the vertices indicated by red dots as shown below. Make the cut shown in yellow.

Extrude the polygons shown in the picture by a value of 1. The actual value doesn't really matter because we might move the polygons later.

The extrusion created extra polys that you don't want but to be able to see them, you have to hide the mirrored half of the mesh. To do this, select the mirrored half of the car, click on the "Display" tab and further down the display panel, click on the "Hide Selected" button.

Now at the front of the remaining half, there is a thin strip of 3 polys that was created by the extrusion you just made select all of them and delete them.

To make things easier, it might be wiser to detach the hood from the car first. So unhide the other half of the mesh, select all the polys that make up half the hood and detach them from the rest of the mesh. Name the hood polys "Hood" and click OK. Now hid the remainder of the mesh, leaving just the hood polys visible.

You will notice that there is now only one half of the hood so mirror it and make sure that you select "Reference" from the Mirror dialog box. Select the front row of vertices and move them backwards a little.

Select the edges at the bottom of the hood as shown below.

Change to the bottom viewport and shift+drag the selected edges diagonally between the X and Y directions as shown below. Adjust the red vertices as shown in the zoomed in areas.

Continuing the hood

Select the two edges shown and extrude them inwards. Weld the two vertices in the green circle.

Now select the remaining edges at the top of the hood and do the same to them. Now your hood should have some depth to it. Now you need to create the ridge that runs down the middle of the hood. Create the cuts shown below.

Select the new polys shown and extrude them by a value of 0.7. There will be a thin line of polys between the two halves that you must delete or you will get two ridges on the hood instead of one.

Now at the front of the remaining half, there is a thin strip of 3 polys that was created by the extrusion you just made select all of them and delete them. Now zoom into the left viewport and get very close to the front of the hood. You will see two vertices that were created by your extrusion. Move these two vertices in the direction of the green arrows below until they are on top of the ones below them. DO NOT WELD THEM! Just leave them on top of each other.

As it is now, the edge around the hood is too round. You have to sharpen the corners of to hood to make it look better. Select all the edges shown in red and chamfer them by a value of 0.1. Add a "Meshsmooth" modifier and set the iterations to 2 and look at what the hood now looks like.

You need to clean up some of the vertices created by the chamfer. Zoom in on the left viewport again and you will notice a triangle of vertices as shown below. Weld the two vertices in the red circle.

Select the edges shown and chamfer them by 0.2. Once again, zoom in on the mesh in the left viewport and perform any vertex cleanup that may be necessary.